In September 1963 Marvel editor Stan Lee introduced a new comic
book called The Uncanny X-Men, which featured a
group of teenage mutants under the tutelage of wheelchair bound
Professor Xavier, himself a mutant possessing telepathic powers.
The Uncanny X-Men was never a big seller, but
in 1975 Marvel started a new line called The X-Men
drawn by Englishman John Byrne and scripted by Chris Claremont.
Imbuing a sense of internationalism into the team there was a German
(NightCrawler), a Russian (Colossus), an African princess (Storm),
a Japanese (Sunfire), a native American (Thunderbird) , and everybodies
immediate favourite the bad tempered Canadian - Wolverine.
As with many other Marvel superheroes, the emphasis was on feeling/being
different from those around them. Mutants possessing strange powers
being persued by normal humanity who looked on them as freaks. This
was a variation of the theme already employed succesfully with Spider-Man
where the "different-ness" simply stemmed from being an
adolescent in an adults world.